Iterative Initial Synchronization in Wireless Communications

Abstract

The family of m-sequences has been widely used for the initial synchronization of generations of wireless systems. We exploit the fact that R chips uniquely and unambiguously determine the entire (2^R - 1) chips of a sequence by designing a Soft-In-Soft-Out (SISO) Recursive Soft Sequence Estimation (RSSE) scheme, relying on similar iterative processing techniques to those of turbo decoders. To elaborate a little further, once R chips have been received, the RSSE scheme augments the soft intrinsic information gleaned from the channel with the aid of the extrinsic information constituted by the previous received chips. Hence, these turbo iterations substantially improve the initial synchronization performance attained.
The scheme advocated is then used for investigating the performance of a large variety of m-sequences as well as of the family of concatenated sequences, which can be generated with the aid of a pair of m-sequences. These concatenated sequences have substantial benefits over the m-sequences. We continued our investigations by tabulating the most attractive m-sequences and concatenated sequences having a large variety of different lengths. The convergence properties of our RSSE schemes were investigated with the aid of EXtrinsic Information Transfer (EXIT) charts.
Finally, as a further refinement we introduced an Automatic Gain Control (AGC) scheme into our RSSE arrangements, which substantially improved its performance.

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ORCID for Lajos Hanzo: orcid.org/0000-0002-2636-5214

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